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Dietary supplementation in the Savanna brown goat. 1. Effect on attainment of puberty in the doe
AnimalReproduction Science, 29 (1992) 157-166
157
Elsevier Science Publishers B.V., Amsterdam
Dietary supplementation in the Savanna Brown goat. 1. Effect on attainment of puberty in the doe O.O.A. Fasanya a, E.C.I. Molokwu b'l, L.O. Eduvie ¢ and N.I. Dim d aDepartment of Animal Production and Fisheries, School of Agriculture and Agricultural Technology, Federal University of Technology, Minna, Niger State, Nigeria bSchool of Veterinary Medicine, Tuskegee University, Tuskegee, 3088, AL, USA CDepartment of Animal Reproduction and Artificial Insemination, National Animal Production Research Institute, Shika, Zaria, Nigeria dDepartment of Animal Science, Faculty of Agriculture, Ahmadu Bello University, Zaria, Nigeria (Accepted 12 June 1991 )
ABSTRACT Fasanya, O.O.A., Molokwu, E.C.I., Eduvie, L.O. and Dim, N.I., 1992. Dietary supplementation in the Savanna Brown goat. 1. Effect on attainment of puberty in the doe. Anita. Reprod. Sci., 29:157166. Twenty nulliparous Savanna Brown (SB) does aged 3-4 months were used to study the effect of dietary supplementation on age and weight at puberty. The animals were randomly distributed into four groups of five animals each. Animals on cottsonseed cake (CSC) (protein) supplement attained puberty at an earlier age ( 190 days) and heavier weight ( 10 kg) than those on maize and CSC (240 days, l0 kg), maize (260 days, 9 kg) or no supplementation (219 days, 10 kg). The mean body weight changes at first standing estrus were not significant (P> 0.05 ), while feed consumption within the group was highly significant (P< 0.05 ). The mean serum progesterone concentration during the prepubertal period was quite low, ranging from non-detectable to 0.1 ng m l - 1. There were elevated levels of peripheral progesterone (above 0.1 ng ml- 1) in all the groups before the first observable estrus. Based on age and body weight changes at the time of onset of puberty in these does, it is concluded that dietary supplementation with CSC can influence the onset of puberty in the SB does, as determined by serum progesterone concentration.
INTRODUCTION
T h e nutritional requirements for reproduction in m o s t species have been a subject o f wide study (Haines et al., 1959; O ' B a n n o n et al., 1966; D u n n et al., 1969; Frobish and Gerrits, 1969; Moore et al., 1973 ). First estrus is considered to represent the onset of puberty in ewe lambs and one or m o r e 'silent ovulations' can precede the first behavioral estrus at Correspondence to: O.A.A. Fasanya, Department of Animal Production and Fisheries, School of Agriculture and Agricultural Technology, Federal University of Technology, Minna, Niger State, Nigeria. ~Present address: Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria. © 1992 Elsevier Science Publishers B.V. All rights reserved 0378-4320/92/$05.00
158
O.O.A. FASANYAET AL.
the beginning of the season in both ewe lambs and mature ewes (Quirke et al., 1985 ). In ewe Iambs, changes in hormonal patterns occur as soon as they approach puberty (Foster et al., 1985 ). The attainment of puberty in the ewe is usually accompanied by increases in basal progesterone concentration. In prepubertal Savanna Brown (SB) goats kept under semi-intensive management systems, the progesterone concentration averaged 0.12 ng m l - 1 and increased to 1.6 ng m l - 1 after the first estrus (Fasanya et al., 1988 ). In Javanese thin-tail sheep, basal progesterone concentrations around puberty averaged 0.16 ng m l - 1 ( Sutama et al., 1988 ). Insufficient dietary energy/protein intake before puberty retards growth and delays puberty in livestock. Energy restriction prevents or slows the maturation process at the hypothalamus-pituitary level (Day et al., 1986). Hence, ovarian steroidogenesis may be compromised in energy/protein-restricted animals. This study was designed to examine the effects of dietary supplementation with maize and cottonseed cake (CSC) given at different ratios on the age and weight at first estrus in nulliparous SB does. MATERIALS AND M E T H O D S
Twenty nulliparous SB does aged 3-4 months were used to determine the effect of dietary supplementation on age and weight at puberty. The animals were distributed randomly into four groups ( A - D ) of five animals each. The animals were all born in the animal experimentation unit of the Federal University of Technology, Minna, Niger State, Nigeria.
Feed supplementation Three dietary supplementations of maize plus CSC, maize and CSC only were provided for animals in Groups A, B and C, respectively. Animals in Group D were not provided with any dietary supplementation. The feed supplementation was provided as bulk feed to the does according to calculated ratios (Table 1 ). The feed supplied per group per day was maintained at 5.0 kg and was weighed daily by 15:00 h, an hour before the animals return from grazing. All animals were allowed to graze freely throughout the day with their dams and they were returned to the pen by 16:00 h for the assigned dietary supplementation. An adequate water supply and salt lick were provided ad libitum. Does within a treatment were group-fed the supplement ad libitum and the feed refused was weighed at 08:00 h the following morning to estimate the amount consumed. Dietary supplementation for Group A was thoroughly mixed maize/CSC so that the does could not preferentially select CSC from the maize. The average daily supplement intake for each group was determined by dividing the sum of the total feed consumed by the number of days for does to exhibit the
DIET IN SAVANNABROWN GOAT. 1. PUBERTY IN DOES
159
TABLE 1 Dietary supplement I for Savanna Brown goats Group
Grazing Maize (energy) Cottonseed cake (protein)
A (E/P) 2
B (E)
C (P)
4+ 1.03 k g d a y - t + 0.127 kg day -~
+ + 1.14 kg day - l -
+ -
D (C)
+ 0.37 kg day -~
1Starch equivalent requirement at an average weight of 16 kg at first kidding was used to calculate the supplement to be provided per day. 2Dietary supplements were isocaloric. E, maize, 6.65% protein provided in a ground form; P, cottonseed cake, 22.92% protein; C, unimproved pasture and shrubs.
first standing estrus. The nitrogen content of maize and CSC was determined by the macro-Kjeldahl digestion method.
Age and body weight changes The does were weighed weekly from the day of dietary supplement to first estrus. The age at which the does within the treatment groups attained puberty was the sum of the period of dietary supplementation and of the nonsupplemented period from birth. However, body weight changes under the different treatment groups were noted from when dietary supplementation commenced. The average daily weight gain for each group was calculated as (Final weight at end of the w e e k - i n i t i a l weight ) / 7 Means of body weight were obtained to give the average daily gain for each treatment group.
Blood sampling Blood (10 ml) was collected by jugular venipuncture every other day. It was cooled immediately and transferred to the laboratory, refrigerated at 4 ° C for 1 h and the serum separated by centrifugation at 5000 rev min -1 for 10 min. The serum was stored immediately at - 2 0 ° C until radioimmunoassayed for progesterone.
160
O.O.A. FASANYA ET AL.
Estrus observation Twice daily observation for estrus was carried out at 08:00 and 18:00 h with intact bucks. Does that stood during mounting by the buck or that were constantly being chased were bred.
Radioimmunoassay The progesterone concentration in peripheral serum was determined by radioimmunoassay with the coated-tube technique. Coated tubes and labeled iodine were supplied by the International Atomic Energy Agency, Vienna, Austria. The m e a n ( + standard error of the mean (s.e.m.)) extraction efficiency was 75 + 4.1% while the sensitivity, defined as twice the standard deviation from the zero standard, was 0.1 ng ml -~. The within- and betweenassay coefficients of variation were 8.5% and 9.6%, respectively.
Statistical analysis The influence of age, body weight changes and feed consumption on the attainment of puberty were determined by performing a one-way analysis of variance as described by Steel and Torrie (1960). A comparison of the average daily gain during the period of dietary supplementation and age at puberty within treatment groups was determined by the same statistical method. Least significant difference was used to establish probability values of observed means within the group.
Onset of puberty The combination of age, body weight change and progesterone concentration at first standing estrus was used to determine when the animals attained puberty. Puberty was defined within each group as when the circulating progesterone concentration was 0.1 ng m l - 1 or more for three or four consecutive samples, even when the doe did not stand to be mounted. RESULTS
Feed consumption The average feed consumption per group to the first observed estrus in these animals is presented in Table 2. The difference in feed consumption between the groups was significant ( P < 0.05 ), with a calculated F value of 116, and the efficiency of feed utilization was greater in Group A than in the other groups. When the means of feed consumption within the various groups were
DIET IN SAVANNABROWNGOAT. 1. PUBERTYIN DOES
161
TABLE2 Consumption of dietary supplement and body weight changes at puberty of Savanna Brown does Group A n Average daily feed supplied (kg)
B 5 5
C
D
5 5
5 5
5
187.0
338.2
-
-
(8:1) 1
Total feed supplement consumed (kg) Average daily supplement intake (kg) Total feed supplement refused (kg) Average daily supplement refusal (kg) Mean initial body weight (kg) Average daily weight gain (kg) Feed efficiency3
294.62 2.34
1.67
2.7
-
305.4 2.55
413.0 3.44
261.8 2.2
-
6.76_+1.35 0.02 98.7
6.3+0.9 0.04 39.4
6.34+0.11 0.06 44.5
6.5+0.75 0.04 ND
IRatio of maize to cottonseed cake. 2Total feed supplement consumed from the start of the study to when first estrus was observed. 3Daily feed intake/daily weight gain. n, number of animals in each group; A, maize/cottonseed cake + grazing; B, maize + grazing; C, cottonseed cake + grazing; D, grazing only; ND, not determined. TABLE3 Mean age and body weight of Savanna Brown does at pubertal estrus Group
n Mean age (days) ~ Mean weights (kg) 2
A
B
C
D
5 240+54 10 _+0.4
5 261_+26 9 _+ 1
5 191_+37 10 + 3
5 219+68 10_+ 0.5
~Differ significantly within the group ( P < 0.05 ). 2Did not differ significantly ( P > 0.05 ). n, number of animals in the group; A, maize/cottonseed cake +grazing; B, maize+grazing; C, cottonseed cake + grazing; D, grazing only.
examined, feed consumption in Group C was slightly better than that in Group A. Average daily gains within all the treatment groups were slight, but gains in Group C exceeded those in Groups A, B and D; average daily supplement intakes in Groups A and C were similar.
Age and body weight changes Does on high-protein dietary supplement attained puberty at an earlier age and heavier body weight than those in the other treatment groups (Table 3 ).
162
O.O.A.FASANYAET AL,
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11
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15
16
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-.10 -'12 -.14 -.16 -'11~
Age
( months
)
Fig. 1. Graph of average daily weight gain over 14 months. 0 , Group D; O, Group C;/x, Group B; @, Group A.
The mean age at puberty for the does consuming maize plus CSC (240 days ), maize (261 days), CSC (190 days) and pasture (220 days) differed ( P < 0 . 0 5 ) , but the mean body weights at first standing estrus between the dietary supplement groups (A, B and C) and the control group (Group D ) were not significantly different ( P > 0.05 ). The average daily gain for each treatment group indicates that the does lost weight within the first 2 months following the introduction of dietary supplementation (Fig. 1 ). This was fol-
DIET IN SAVANNA BROWN GOAT. 1. PUBERTY IN DOES
163
lowed by a gradual increase in body weight gain which was maintained after the does began estrous activity.
Progesterone concentration Changes in peripheral progesterone concentrations before and after puberty are presented in Fig. 2. The mean progesterone concentration for each dietary supplementation was low during the prepubertal stages of development. The does on dietary supplementation A and C constantly had circulating progesterone concentrations consistently greater than 0.1 ng m l - 1 before the animals stood to be mounted. However, in Groups B and D, the level of detectable peripheral progesterone before the does stood to be mounted was much lower than 0.1 ng m l - 1. In Group A, there were short spikes of elevated progesterone with an apparent luteal phase shortly before the day of first estrus. This was not evident with does in Group C where the mean peripheral progesterone was maintained near 0.1 ng m l - ~before the animals stood to be mounted. The does in Group B exhibited a pronounced luteal phase just before the animals were mounted. Generally, there were elevated levels of progesterone in all the groups before the first overt estrus. DISCUSSION
Although feed consumption by the does in Groups A and C was similar, animals in Group C had a greater average daily gain (Table 2 ) and, thus, an increased growth rate compared with the other groups. The efficiency of feed utilization obtained is indicative of a relatively poor pattern of growth and maturation in these animals during the prepubertal period, which is clearly demonstrated in the average daily weight gain obtained. Dyrmundsson ( 1973 ) had indicated that it is possible to reduce the age of attainment of puberty by providing dietary supplementation. It would appear that for the brown goats the protein diet might be acting with physiologic growth parameters to enhance the chances of the ovaries becoming functional at an early age, therefore allowing first estrus to be exhibited. The results of this study show that animals on the pure CSC supplement were younger and heavier at the first pubertal estrus. This is in agreement with the results of Taylor and Merill (1977) who observed that the body weight gain in Angora kids on corn supplement was less than that of those on CSC and pasture. It seems that a high-protein diet can influence the age of attainment of puberty, but not affect body weight changes. This observation also agrees with that in cattle, where Penzhorn ( 1975 ) and Shokamoto et al. ( 1975 ) noted that the nutritional level does affect age at puberty, but will not influence body weight changes. The progesterone profile of the does in this study showed that those on
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oi
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DIET IN SAVANNA BROWN GOAT. 1. PUBERTY IN DOES
165
dietary supplementations A and C had increased levels of peripheral progesterone even before they stood to be mounted. This indicates that there could have been some level of ovarian function before sampling commenced. The peaks of progesterone concentration before mounting for the does in Group A showed that estrual activity existed in these animals before they exhibited overt estrus. The short luteal phases of progesterone noticed in Groups A, B and D are also similar to those reported for ewes by Sebestian et al. (1984) and Oyedipe et al. (1986). This implies that some short estrus cycles and 'silent ovulations' could have occurred in the does before they were mounted. The interplay of factors such as size, body weight, age, nutrition and breed on puberty is not in doubt, but the relative role of each of these factors is a measure of improvement in the reproductive activity which has not been documented earlier for SB goats. Since the level of dietary supplementation significantly affected the age at which the first overt estrus was exhibited, and not necessarily the body weight, it is clear that there could be a predetermined size at which puberty could occur, as was suggested for cattle (Oyedipe et al., 1982 ). Although weight changes from birth in the kids used in this study were not used to examine the pattern of change before supplementation started, there is no doubt that this could have an influence on the rate of growth and subsequent reproductive performance of these animals. The dietary supplementation in Groups A and C allowed these animals to undergo fairly good rapid growth, hence attaining a good size and weight at an early age. It is, therefore, concluded that dietary supplementation with CSC (high protein) would enhance the chances of SB does reaching puberty at an earlier stage in life. ACKNOWLEDGMENT
This project was supported by funds from the Board of Research of the Federal University of Technology, Minna.
REFERENCES Day, M.L., Imalawa, K., Zalesky, D.D., Kittok, R.J. and Kinder, J.E., 1986. Effects of restriction of dietary energy intake during the prepubertal period of secretion of luteinizing hormone and responsiveness of the pituitary to luteinizing hormone-releasing hormone in heifers. J. Anim. Sci., 62: 1641-1648. Dunn, T.G,, Ingalls, J.E., Zimmerman, D.R. and Wiltbank, J.N., 1969. Reproductive performance of 2-year old Hereford and Angus heifers as influenced by pre- and post calving energy intake. J. Anim. Sci., 29: 719-776. Dyrmundsson, O.R., 1973. Puberty and early reproductive performance in sheep. I. Ewe lambs. Anim. Breed. Abstr., 41: 273-289. Fasanya, O.O.A., Molokwu, E.C.I., Adeyemo, O. and Umaru, I.I., 1988. Onset of puberty in the
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Savanna Brown goat under semi-intensive management system. Proceedings of the VI World Conference on Animal Production, Helsinki, p. 589. Foster, D.L., Yelson, S.M. and Olster, D.M., 1985. Internal and external determinants of the timing of puberty in the female. J. Reprod. Fertil., 75: 327-344. Frobish, L.T. and Gerrits, R.J., 1969. Effect of energy intake and oestrus synchronization on reproductive performance of gilts. J. Anim. Sci., 37: 728-733. Haines, C.E., Warnick, A.C. and Wallace, H.D., 1959. The effect of two levels of energy intake on reproductive phenomenon in Duroc Jersey gilts. J. Anim. Sci., 18: 347. Moore, C.P., Dutt, R.H., Hays, V.W. and Griwell, G.L., 1973. Influence of one-day or conventional flushing on ovulation rate and litter size at 28 days gestation in gilts. J. Anim. Sci., 37: 734-738. O'Bannon, R.H., Wallace, H.D., Warnick, A.C. and Combs, C.E., 1966. Influence of energy intake on reproductive performance of gilts. J. Anim. Sci., 25: 660. Oyedipe, E.O., Buvanendran, V. and Eduvie, L.O., 1982. Some factors affecting the reproductive performance of White Fulani (Bunaji) cattle. Trop. Agric. (Trinidad), 59: 231-234. Oyedipe, E.O., Pathiraja, N., Edqvist, L.E. and Buvanendran, V., 1986. Onset of puberty and oestrus cycle phenomena in Y'ankassa ewes as monitored by plasma progesterone concentrations. Anita. Reprod. Sci., 12: 195-199. Penzhorn, E.J., 1975. Wintering levels and reproduction in Afrikander heifers. Agroanimal, 7: 49-59. Quirke, J.F., Stabenfeldt, G.H. and Bradford, C.E., 1985. Onset of puberty and duration of breeding season of Suffolk, Rambouillet, Finish Landrace, Dorset and Finn-Dorset ewe lambs. J. Anim. Sci., 60: 1463-1469. Sebestian, A.L., Demiquel, M.A., Brunet, A.C. and Garca, T.P., 1984. Attainment of puberty in Manchega ewe Iambs born in fall and stimulated by rams. Anim. Breed. Abstr., 52: 232-233. Shokamoto, S., Imaizum, E. and Shijiamaya, K., 1975. The effect of different planes of nutrition during growth in the productivity of Holstein cows. III. Growth to calving for two groups of cows calving at the same body weights. Anim. Breed. Abstr., 43: 676. Steel, R.G.D. and Torrie, J.H., 1960. Principles and Procedures of Statistics. A Biometrical Approach. 2rid Edn. McGraw-Hill, New York, pp. 67-87. Sutama, I.K., Edey, T.N. and Fletcher, I.C., 1988. Oestrus cycle dynamics in peri-pubertal and mature Javanese thin-tail sheep. Anita. Reprod. Sci., 16: 61-70. Taylor, C.A., Jr. and Merill, L.B., 1977. Feeding three supplements to Angora kids. Sheep and Goat, Wool and Mohair. Tex. Agric. Exp. Stn. Bull., 22-25.
157
Elsevier Science Publishers B.V., Amsterdam
Dietary supplementation in the Savanna Brown goat. 1. Effect on attainment of puberty in the doe O.O.A. Fasanya a, E.C.I. Molokwu b'l, L.O. Eduvie ¢ and N.I. Dim d aDepartment of Animal Production and Fisheries, School of Agriculture and Agricultural Technology, Federal University of Technology, Minna, Niger State, Nigeria bSchool of Veterinary Medicine, Tuskegee University, Tuskegee, 3088, AL, USA CDepartment of Animal Reproduction and Artificial Insemination, National Animal Production Research Institute, Shika, Zaria, Nigeria dDepartment of Animal Science, Faculty of Agriculture, Ahmadu Bello University, Zaria, Nigeria (Accepted 12 June 1991 )
ABSTRACT Fasanya, O.O.A., Molokwu, E.C.I., Eduvie, L.O. and Dim, N.I., 1992. Dietary supplementation in the Savanna Brown goat. 1. Effect on attainment of puberty in the doe. Anita. Reprod. Sci., 29:157166. Twenty nulliparous Savanna Brown (SB) does aged 3-4 months were used to study the effect of dietary supplementation on age and weight at puberty. The animals were randomly distributed into four groups of five animals each. Animals on cottsonseed cake (CSC) (protein) supplement attained puberty at an earlier age ( 190 days) and heavier weight ( 10 kg) than those on maize and CSC (240 days, l0 kg), maize (260 days, 9 kg) or no supplementation (219 days, 10 kg). The mean body weight changes at first standing estrus were not significant (P> 0.05 ), while feed consumption within the group was highly significant (P< 0.05 ). The mean serum progesterone concentration during the prepubertal period was quite low, ranging from non-detectable to 0.1 ng m l - 1. There were elevated levels of peripheral progesterone (above 0.1 ng ml- 1) in all the groups before the first observable estrus. Based on age and body weight changes at the time of onset of puberty in these does, it is concluded that dietary supplementation with CSC can influence the onset of puberty in the SB does, as determined by serum progesterone concentration.
INTRODUCTION
T h e nutritional requirements for reproduction in m o s t species have been a subject o f wide study (Haines et al., 1959; O ' B a n n o n et al., 1966; D u n n et al., 1969; Frobish and Gerrits, 1969; Moore et al., 1973 ). First estrus is considered to represent the onset of puberty in ewe lambs and one or m o r e 'silent ovulations' can precede the first behavioral estrus at Correspondence to: O.A.A. Fasanya, Department of Animal Production and Fisheries, School of Agriculture and Agricultural Technology, Federal University of Technology, Minna, Niger State, Nigeria. ~Present address: Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria. © 1992 Elsevier Science Publishers B.V. All rights reserved 0378-4320/92/$05.00
158
O.O.A. FASANYAET AL.
the beginning of the season in both ewe lambs and mature ewes (Quirke et al., 1985 ). In ewe Iambs, changes in hormonal patterns occur as soon as they approach puberty (Foster et al., 1985 ). The attainment of puberty in the ewe is usually accompanied by increases in basal progesterone concentration. In prepubertal Savanna Brown (SB) goats kept under semi-intensive management systems, the progesterone concentration averaged 0.12 ng m l - 1 and increased to 1.6 ng m l - 1 after the first estrus (Fasanya et al., 1988 ). In Javanese thin-tail sheep, basal progesterone concentrations around puberty averaged 0.16 ng m l - 1 ( Sutama et al., 1988 ). Insufficient dietary energy/protein intake before puberty retards growth and delays puberty in livestock. Energy restriction prevents or slows the maturation process at the hypothalamus-pituitary level (Day et al., 1986). Hence, ovarian steroidogenesis may be compromised in energy/protein-restricted animals. This study was designed to examine the effects of dietary supplementation with maize and cottonseed cake (CSC) given at different ratios on the age and weight at first estrus in nulliparous SB does. MATERIALS AND M E T H O D S
Twenty nulliparous SB does aged 3-4 months were used to determine the effect of dietary supplementation on age and weight at puberty. The animals were distributed randomly into four groups ( A - D ) of five animals each. The animals were all born in the animal experimentation unit of the Federal University of Technology, Minna, Niger State, Nigeria.
Feed supplementation Three dietary supplementations of maize plus CSC, maize and CSC only were provided for animals in Groups A, B and C, respectively. Animals in Group D were not provided with any dietary supplementation. The feed supplementation was provided as bulk feed to the does according to calculated ratios (Table 1 ). The feed supplied per group per day was maintained at 5.0 kg and was weighed daily by 15:00 h, an hour before the animals return from grazing. All animals were allowed to graze freely throughout the day with their dams and they were returned to the pen by 16:00 h for the assigned dietary supplementation. An adequate water supply and salt lick were provided ad libitum. Does within a treatment were group-fed the supplement ad libitum and the feed refused was weighed at 08:00 h the following morning to estimate the amount consumed. Dietary supplementation for Group A was thoroughly mixed maize/CSC so that the does could not preferentially select CSC from the maize. The average daily supplement intake for each group was determined by dividing the sum of the total feed consumed by the number of days for does to exhibit the
DIET IN SAVANNABROWN GOAT. 1. PUBERTY IN DOES
159
TABLE 1 Dietary supplement I for Savanna Brown goats Group
Grazing Maize (energy) Cottonseed cake (protein)
A (E/P) 2
B (E)
C (P)
4+ 1.03 k g d a y - t + 0.127 kg day -~
+ + 1.14 kg day - l -
+ -
D (C)
+ 0.37 kg day -~
1Starch equivalent requirement at an average weight of 16 kg at first kidding was used to calculate the supplement to be provided per day. 2Dietary supplements were isocaloric. E, maize, 6.65% protein provided in a ground form; P, cottonseed cake, 22.92% protein; C, unimproved pasture and shrubs.
first standing estrus. The nitrogen content of maize and CSC was determined by the macro-Kjeldahl digestion method.
Age and body weight changes The does were weighed weekly from the day of dietary supplement to first estrus. The age at which the does within the treatment groups attained puberty was the sum of the period of dietary supplementation and of the nonsupplemented period from birth. However, body weight changes under the different treatment groups were noted from when dietary supplementation commenced. The average daily weight gain for each group was calculated as (Final weight at end of the w e e k - i n i t i a l weight ) / 7 Means of body weight were obtained to give the average daily gain for each treatment group.
Blood sampling Blood (10 ml) was collected by jugular venipuncture every other day. It was cooled immediately and transferred to the laboratory, refrigerated at 4 ° C for 1 h and the serum separated by centrifugation at 5000 rev min -1 for 10 min. The serum was stored immediately at - 2 0 ° C until radioimmunoassayed for progesterone.
160
O.O.A. FASANYA ET AL.
Estrus observation Twice daily observation for estrus was carried out at 08:00 and 18:00 h with intact bucks. Does that stood during mounting by the buck or that were constantly being chased were bred.
Radioimmunoassay The progesterone concentration in peripheral serum was determined by radioimmunoassay with the coated-tube technique. Coated tubes and labeled iodine were supplied by the International Atomic Energy Agency, Vienna, Austria. The m e a n ( + standard error of the mean (s.e.m.)) extraction efficiency was 75 + 4.1% while the sensitivity, defined as twice the standard deviation from the zero standard, was 0.1 ng ml -~. The within- and betweenassay coefficients of variation were 8.5% and 9.6%, respectively.
Statistical analysis The influence of age, body weight changes and feed consumption on the attainment of puberty were determined by performing a one-way analysis of variance as described by Steel and Torrie (1960). A comparison of the average daily gain during the period of dietary supplementation and age at puberty within treatment groups was determined by the same statistical method. Least significant difference was used to establish probability values of observed means within the group.
Onset of puberty The combination of age, body weight change and progesterone concentration at first standing estrus was used to determine when the animals attained puberty. Puberty was defined within each group as when the circulating progesterone concentration was 0.1 ng m l - 1 or more for three or four consecutive samples, even when the doe did not stand to be mounted. RESULTS
Feed consumption The average feed consumption per group to the first observed estrus in these animals is presented in Table 2. The difference in feed consumption between the groups was significant ( P < 0.05 ), with a calculated F value of 116, and the efficiency of feed utilization was greater in Group A than in the other groups. When the means of feed consumption within the various groups were
DIET IN SAVANNABROWNGOAT. 1. PUBERTYIN DOES
161
TABLE2 Consumption of dietary supplement and body weight changes at puberty of Savanna Brown does Group A n Average daily feed supplied (kg)
B 5 5
C
D
5 5
5 5
5
187.0
338.2
-
-
(8:1) 1
Total feed supplement consumed (kg) Average daily supplement intake (kg) Total feed supplement refused (kg) Average daily supplement refusal (kg) Mean initial body weight (kg) Average daily weight gain (kg) Feed efficiency3
294.62 2.34
1.67
2.7
-
305.4 2.55
413.0 3.44
261.8 2.2
-
6.76_+1.35 0.02 98.7
6.3+0.9 0.04 39.4
6.34+0.11 0.06 44.5
6.5+0.75 0.04 ND
IRatio of maize to cottonseed cake. 2Total feed supplement consumed from the start of the study to when first estrus was observed. 3Daily feed intake/daily weight gain. n, number of animals in each group; A, maize/cottonseed cake + grazing; B, maize + grazing; C, cottonseed cake + grazing; D, grazing only; ND, not determined. TABLE3 Mean age and body weight of Savanna Brown does at pubertal estrus Group
n Mean age (days) ~ Mean weights (kg) 2
A
B
C
D
5 240+54 10 _+0.4
5 261_+26 9 _+ 1
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examined, feed consumption in Group C was slightly better than that in Group A. Average daily gains within all the treatment groups were slight, but gains in Group C exceeded those in Groups A, B and D; average daily supplement intakes in Groups A and C were similar.
Age and body weight changes Does on high-protein dietary supplement attained puberty at an earlier age and heavier body weight than those in the other treatment groups (Table 3 ).
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The mean age at puberty for the does consuming maize plus CSC (240 days ), maize (261 days), CSC (190 days) and pasture (220 days) differed ( P < 0 . 0 5 ) , but the mean body weights at first standing estrus between the dietary supplement groups (A, B and C) and the control group (Group D ) were not significantly different ( P > 0.05 ). The average daily gain for each treatment group indicates that the does lost weight within the first 2 months following the introduction of dietary supplementation (Fig. 1 ). This was fol-
DIET IN SAVANNA BROWN GOAT. 1. PUBERTY IN DOES
163
lowed by a gradual increase in body weight gain which was maintained after the does began estrous activity.
Progesterone concentration Changes in peripheral progesterone concentrations before and after puberty are presented in Fig. 2. The mean progesterone concentration for each dietary supplementation was low during the prepubertal stages of development. The does on dietary supplementation A and C constantly had circulating progesterone concentrations consistently greater than 0.1 ng m l - 1 before the animals stood to be mounted. However, in Groups B and D, the level of detectable peripheral progesterone before the does stood to be mounted was much lower than 0.1 ng m l - 1. In Group A, there were short spikes of elevated progesterone with an apparent luteal phase shortly before the day of first estrus. This was not evident with does in Group C where the mean peripheral progesterone was maintained near 0.1 ng m l - ~before the animals stood to be mounted. The does in Group B exhibited a pronounced luteal phase just before the animals were mounted. Generally, there were elevated levels of progesterone in all the groups before the first overt estrus. DISCUSSION
Although feed consumption by the does in Groups A and C was similar, animals in Group C had a greater average daily gain (Table 2 ) and, thus, an increased growth rate compared with the other groups. The efficiency of feed utilization obtained is indicative of a relatively poor pattern of growth and maturation in these animals during the prepubertal period, which is clearly demonstrated in the average daily weight gain obtained. Dyrmundsson ( 1973 ) had indicated that it is possible to reduce the age of attainment of puberty by providing dietary supplementation. It would appear that for the brown goats the protein diet might be acting with physiologic growth parameters to enhance the chances of the ovaries becoming functional at an early age, therefore allowing first estrus to be exhibited. The results of this study show that animals on the pure CSC supplement were younger and heavier at the first pubertal estrus. This is in agreement with the results of Taylor and Merill (1977) who observed that the body weight gain in Angora kids on corn supplement was less than that of those on CSC and pasture. It seems that a high-protein diet can influence the age of attainment of puberty, but not affect body weight changes. This observation also agrees with that in cattle, where Penzhorn ( 1975 ) and Shokamoto et al. ( 1975 ) noted that the nutritional level does affect age at puberty, but will not influence body weight changes. The progesterone profile of the does in this study showed that those on
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dietary supplementations A and C had increased levels of peripheral progesterone even before they stood to be mounted. This indicates that there could have been some level of ovarian function before sampling commenced. The peaks of progesterone concentration before mounting for the does in Group A showed that estrual activity existed in these animals before they exhibited overt estrus. The short luteal phases of progesterone noticed in Groups A, B and D are also similar to those reported for ewes by Sebestian et al. (1984) and Oyedipe et al. (1986). This implies that some short estrus cycles and 'silent ovulations' could have occurred in the does before they were mounted. The interplay of factors such as size, body weight, age, nutrition and breed on puberty is not in doubt, but the relative role of each of these factors is a measure of improvement in the reproductive activity which has not been documented earlier for SB goats. Since the level of dietary supplementation significantly affected the age at which the first overt estrus was exhibited, and not necessarily the body weight, it is clear that there could be a predetermined size at which puberty could occur, as was suggested for cattle (Oyedipe et al., 1982 ). Although weight changes from birth in the kids used in this study were not used to examine the pattern of change before supplementation started, there is no doubt that this could have an influence on the rate of growth and subsequent reproductive performance of these animals. The dietary supplementation in Groups A and C allowed these animals to undergo fairly good rapid growth, hence attaining a good size and weight at an early age. It is, therefore, concluded that dietary supplementation with CSC (high protein) would enhance the chances of SB does reaching puberty at an earlier stage in life. ACKNOWLEDGMENT
This project was supported by funds from the Board of Research of the Federal University of Technology, Minna.
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