J.A. Delgadillo

Evidence for an annual reproductive rhythm independent of food availability in male creole goats in subtropical northern mexico

The aim of this study was to determine if there is a seasonal pattern of sexual activity dependent on food availability in male Creole goats in subtropical Mexico. The study was conducted in the Laguna Region in the State of Coahuila, Mexico (26 degrees N). Male Creole goats (n = 8) were kept in a shed, fed alfalfa ad libitum and given 200 g of concentrate daily throughout the study. Live weight and testicular weight were determined every 2 wk. Sexual behavior and sperm production were determined monthly. Blood samples were obtained weekly to determine testosterone plasma concentrations. All variables were subjected to sinusoidal modeling procedures and showed important seasonal variations (P < 0.0001) with different phase angles for body weight, testicular weight and testosterone plasma concentrations. The nadir of live weight occurred in November and the peak in May. The lowest testicular weight (90 g) and testosterone plasma concentrations (0.1 ng/mL) were observed in January and February, respectively, while the peaks were observed in July and August (145 g and 10 ng/mL, respectively). Ejaculation latency also varied during the study, being low between May and November (96 sec) and reaching a peak in April (183 sec). Minimum number of spermatozoa per ejaculate occurred between February and April (1.4 x 10(9) cells/ejaculate) while the maximum number was observed between May and September (2.8 x 10(9) spermatozoa/ejaculate). Progressive sperm motility was low between January and April (3.04 on average) and high between May and November (about 3.55 on average). The percentage of live spermatozoa diminished between January and April (68% in April) and then increased to values around 80% between May and November. These results lead us to conclude that male Creole goats in Northern Mexico, fed constantly throughout the year, exhibit seasonality in their reproductive activity. Intense sexual activity occurred between May and December.

Decrease in the seasonality of sexual behavior and sperm production in bucks by exposure to short photoperiodic cycles

Bucks show seasonal variation in their body weight and sexual activity. Three groups of six Alpine and Saanen bucks were used over two consecutive years to investigate if rapid alternations between long and short days could abolish this seasonal variation. The control group was kept under natural annual daylength, while the experimental groups were exposed to alternations of either 1 month of 16L:8D and 1 month of 8L:16D (2-month treatment) or to 2 months of 16L:8D and 2 months of 8L:16D (4-month treatment). In the control group, body weight, sexual behavior, testicular weight and sperm production showed important seasonal variations: body weight decreased between September and January by about 7 kg; refusal to ejaculate went up to 25% in August; testicular weight varied from 103 +/- 2 g (March) to 149 +/- 7 g (October). In contrast, seasonal variations of these parameters decreased in the two experimental groups. In the 2-month treatment group, testicular weight increased from 134 +/- 7 (March) to 148 +/- 8 g (October); while in the 4-month treatment group it increased from 123 +/- 10 to 138 +/- 12 g, respectively; in the same period, the two experimental groups of bucks produced a larger total number of spermatozoa per ejaculate (6.3 +/- 0.3 x 10(9); 2-month treatment and 7.2 +/- 0.3; 4-month treatment) than in the control group (4.2 +/- 0.4). We conclude that rapid alternations between long and short days decreased seasonality in the sexual activity of bucks.

Reproductive seasonality in female goats adapted to a subtropical environment persists independently of food availability.

The aim of this study was to determine whether the seasonal change in food availability provides a predictive cue that synchronizes the breeding season in goats adapted to the subtropical conditions of Northern Mexico. Groups of multiparous intact (n=7) and ovariectomized does bearing a subcutaneous implant constantly releasing estradiol-l7 beta (OVX+E; n=12) were allocated in two pens and received a constant amount of feed. Another group of OVX+E does (n=10) was incorporated into a flock raised under natural grazing conditions with seasonal fluctuations in food availability. Blood samples were taken twice weekly. Ovulation of intact goats was inferred from plasma progesterone levels. In OVX+E does plasma levels of LH were measured. Intact does displayed seasonal variations in ovulation and the breeding season lasted from September to February. OVX+E goats displayed large seasonal variations in LH secretion regardless of whether they were fed constantly indoors or kept under natural grazing conditions (P<0.0001). The mean date of increase in LH secretion varied between years (P<0.0001) but did not differ between groups (naturally grazed: August 13+/-10 days; constantly fed: August 26+/-10 days). In contrast, the seasonal decline in LH secretion differed between groups: it was consistently delayed in constantly fed animals compared to those feeding naturally (naturally grazed: January 28+/-4 days; constantly fed: February 24+/-6 days, group effect, P<0.01). These results show that local female goats from subtropical Mexico display large reproductive seasonality independently of food availability.

Abolition of seasonal variations in semen quality and maintenance of sperm fertilizing ability by photoperiodic cycles in goat bucks

Goat bucks show large seasonal variations in semen quality mainly influenced by photoperiodic changes. Minimum percentage of motile sperm cells and velocity occur during spring and summer. Three groups of Alpine and Saanen bucks (n = 6 in each group) were used to determine whether rapid alternations between long and short days were able to abolish seasonal variations in semen quality. One group remained in open sheds under natural day length (An) which varied from 16 h light (June) to 8 h light per day (December). The first experimental group (2Mo) was exposed to alternations between 1 month of long days (16L:8D) and 1 month of short days (8L:16D) and the second one (4Mo) to alternations between 2 months of long days (16L:8D) and 2 months of short days (8L:16D), during two consecutive years. All parameters of semen quality before freezing and after thawing varied with time in the three groups (P < 0.05). Interaction between group and time was also detected for five parameters out of six (P < 0.001), indicating that groups varied differently with time. Semen quality in the experimental groups was not affected by prevailing day length. As expected, in group An, the percentage of motile sperm and sperm motility score (0–5) before freezing and after thawing decreased during the nonbreeding season (March to August; minimum in August: 37.8% and 2.4 score before freezing) compared to the breeding season (September to February; maximum in January: 66.3% and 3.6 score before freezing). The production of semen doses available for A.I. also decreased during this period. In contrast, in the two experimental groups the decrease in sperm quality during this period was prevented. In these groups, the percentage of motile sperm and sperm motility before freezing and after thawing remained at the same level as observed in group An during the natural breeding season. Abolition of seasonal variation in semen quality led to production of 69.0 and 54.7% more A.I. doses in groups 2Mo and 4Mo than in group Am. Sperm fertility in the three groups did not show significant differences (59.4% of kiddings in 1599 goats from 58 flocks). It was concluded that, in goat bucks, alternations between long and short days abolished the seasonal variation in semen quality without altering sperm fertility.

Nutritional supplementation improves ovulation and pregnancy rates in female goats managed under natural grazing conditions and exposed to the male effect

Two experiments were conducted to determine if nutritional supplementation improved ovulation and pregnancy rates in female goats managed under grazing conditions and submitted to the male effect. In Experiment 1, one group of does did not receive nutritional supplementation, while the other group was supplemented daily for 7 days starting at the time when the males were introduced to the females. The ovulation rate at the second male-induced ovulation was greater (P<0.05) in supplemented (2.0+/-0.1) than in non-supplemented (1.6+/-0.1) does. For Experiment 2, female goats were supplemented for 0, 7, 14 or 28 days, starting 9 days following buck introduction. The proportion of does that were pregnant in the group supplemented for 28 days was greater (P<0.05) than in the non-supplemented group, but did not differ from 14-day and the 7-day supplemented groups. The proportion of pregnant does was greater (P<0.05) in the group supplemented for 14 days compared to the group supplemented for 7 days and the non-supplemented group. These latter two groups did not differ (P>0.05). In conclusion, feed supplementation for 7 days, starting at the time when males were introduced increased ovulation rate and feed supplementation for 14 or 28 days starting 9 days after males were introduced improved pregnancy rates in goats managed under grazing conditions and exposed to males.

Management of goat reproduction and insemination for genetic improvement in France.

Reproductive seasonality observed in all breeds of goats originating from temperate latitudes and in some breeds from subtropical latitudes can now be controlled by artificial changes in photoperiod. Short days stimulate sexual activity, while long days inhibit it. This knowledge has allowed the development of photoperiodic treatments to control sexual activity in goats, for both the buck and doe. In the French intensive milk production system, goat AI plays an important role to control reproduction and, in conjunction with progeny testing, to improve milk production. Most dairy goats are inseminated out of the breeding season with deep frozen semen, after induction of oestrus and ovulation by hormonal treatments. This protocol provides a kidding rate of approximately 65%. New breeding strategies have been developed, based on the buck effect associated with AI, to reduce the use of hormones. With the development of insemination with frozen semen, a classical selection programme was set up, including planned mating, progeny testing and the diffusion of proved sires by inseminations in herds. Functional traits have become important for efficient breeding schemes in the dairy goat industries. Based on knowledge gained over the past decade, the emphasis in selective breeding has been placed on functional traits related to udder morphology and health. New windows have been opened based on new molecular tools, allowing the detection and mapping of genes of economic importance.

Male effect in seasonally anovulatory lactating goats depends on the presence of sexually active bucks, but not estrous females

A study was conducted in subtropical northern Mexico (26 degrees N) to determine whether the presence of estrous females can improve the response of seasonally anovulatory goats to the introduction of bucks in the group. The induction of estrous activity was studied in three groups of anovulatory lactating goats during seasonal anestrus. These females were of the Mexican Creole breed. In the control group (sexually inactive (SI), n = 20), two control (SI) bucks exposed to normal seasonal daylength variations were used. In the second group (SI + E, n = 20 + 3), two control males were also used, but in addition, three females of the group were in estrus at the time of male introduction. In the third group (sexually active, SA + E, n = 19 + 4), anovulatory females were exposed to two bucks made sexually active by exposure to 2.5 months of long days (16L:8D) followed by two subcutaneous 18 mg melatonin implants, and four estrous females were also present when introducing the bucks. In all groups, males were introduced on 15 March and estrous detection was conducted twice daily for 15 days. The sexual activity of the bucks was observed from 08:00 to 10:00 h during the first five days of exposure to females. More females displayed estrous behavior in the first 15 days following the introduction of the males in the SA + E group (18/19) as compared with the SI or SI + E groups (2/20 and 0/20, respectively; P < 0.001). No difference was observed between the two latter groups. Thirteen females of SA + E group showed a second estrus between days 6 and 11 (short estrous cycle duration: 5.4 +/- 0.4 days). By contrast, in the SI group none showed a second estrus. The sexual behavior of the males in the SA + E group was greater as compared with that of the males in SI and SI + E groups (over 80% of the total sexual activity recorded in the three groups; P < 0.001). By contrast, no differences were found between SI and SI + E males. These results indicate that the presence of estrous females alone at the time of buck introduction is not sufficient to induce an adequate stimulation of seasonally inactive males. The use of sexually active bucks is necessary to induce reproductive activity in anovulatory females, whereas preparation of the bucks with long days followed by melatonin implants allows them to gain such a capacity.

Ovulatory activity of female goats adapted to the subtropics is responsive to photoperiod

The objective of this study was to determine whether reproductive seasonality of local well-fed female goats from subtropical Mexico (26 degrees N) can be controlled by photoperiod. The control group (n=12) remained in an open pen under natural photoperiod variations. The two experimental groups (n=8 each) were placed in light-proof rooms and exposed for 2 yr to alternations of 3 months of long days and 3 months of short days. One group was first exposed to long days, Group 1, and the other one to short days, Group 2. Blood samples were obtained twice a week to determine ovulation status by progesterone plasma concentrations. Goats from the control group displayed a seasonality of ovulations. The mean (+/-SEM) dates of the onset and end of the ovulations were September 10+/-5 d and February 16+/-4 d, respectively. In contrast, in both experimental groups, ovulations were modified (P<0.05) by the photoperiodic treatments such that ovulations started and ended during short and long days, respectively. In Groups 1 and 2, ovulations started 67+/-2 and 66+/-2 d (P>0.05), respectively, after the transfer from long to short days. In contrast, the timing of the cessation of ovulations after the transfer from short to long days differed (P<0.05) between groups (19+/-3 and 31+/-3 d for Groups 1 and 2, respectively). Local female goats from subtropical Mexico are, therefore, sensitive to photoperiodic changes that they are exposed to at this latitude and this environmental cue may control the timing of the breeding season in natural conditions.

The ovulation rate in anoestrous female goats managed under grazing conditions and exposed to the male effect is increased by nutritional supplementation

This experiment was conducted to determine if feed supplementation before exposure of anoestrous does to males increases ovulation rate. Does (n=50) grazing natural vegetation were divided into two groups (n=25). One group received no feed supplementation, while the other was supplemented daily, with a mixture of 950 g of alfalfa hay, 290 g of rolled corn and 140 g of soy bean per animal for 7 days before exposure to bucks. On April 7, all females were exposed to four adult sexually active bucks (two per group) for 15 days. The ovulation rate at the ovulation detected within 5 days of exposure to males, assessed by transrectal ultrasonography, was greater (P<0.05) in supplemented (1.6+/-0.2) than in non-supplemented females (1.0+/-0.2). In contrast, ovulation rate at the subsequent ovulation, detected between days 6 and 15 of contact with males, was not different (P>0.05) between supplemented (1.3+/-0.1) and non-supplemented females (1.3+/-0.2). Feed supplementation 7 days before exposure to sexually active bucks of females managed under grazing conditions increased their ovulation rate at the first male-induced ovulation but the stimulatory effect of supplementation did not persist and was not observed at the subsequent ovulation.

Length of postpartum anestrus in goats in subtropical Mexico: effect of season of parturition and duration of nursing

The aim of this study was to determine whether season of birth and length of nursing affected the duration of postpartum anestrus in Creole female goats maintained on a constant plane of nutrition in subtropical Mexico. Three experiments were conducted in the Laguna region in the State of Coahuila, Mexico (26 degrees N). In the first experiment, 34 goats gave birth in January; in the second, 31 females gave birth in May; and in the third, 22 goats kidded in October. At parturition, females were allocated to 1 of 3 groups based on body weight and date of parturition: kids were weaned at 2, 30 or 90 d according to their group. After weaning, females were milked manually once a day until the end of the study. All animals were kept in a shed and were fed alfalfa ad libitum and given 200 g of concentrate daily. Starting 1 wk after parturition, estrous behavior was detected twice daily using an apron-bearing male, and blood samples were obtained twice weekly to determine ovarian activity from the plasma progesterone levels. A strong effect of month of parturition was found on the duration of postpartum anestrus (P < 0.0001), which was longer in females kidding in January (about 200 d) than in those kidding in May (about 100 d) or October (about 50 d). A tendency for an interaction between season of parturition and length of nursing was observed in the length of anovulation (P < 0.07): for parturition in October, anestrus was longer when kids were weaned after 90 d than after 2 or 30 d (P < 0.01). Season of parturition also affected dates of reinitiation of ovulatory and estrous activity (P < 0.001). Proportions of normal, short and long cycles and of associations between estrous and ovulations were not influenced by season of parturition or the age of weaning. These data demonstrate that in subtropical latitudes, season of parturition can dramatically influence the duration of postpartum anestrus independently of the availability of food.