PSIV-1 Distribution of kidding dates as an indicator of buck-induced estrus in cycling meat goat does.

Abstract Meat goat operations could benefit from the ability to effectively shorten breeding seasons and in turn shorten kidding seasons to enhance herd management. Buck-induced estrus could facilitate a reduction of time required to maintain service sires in the doe herd. The use of bucks to induce estrus has traditionally been applied to does in seasonal anestrus. During a normal short-day breeding season in the absence of the buck effect, 5% of does within a herd are expected, on average, to come in to heat daily. This study looked at the relationship between expected and observed kidding dates within the first 7 and 10 days of the kidding season. The start of each kidding season was determined based on the date that service sires were placed with the does and using a 150-day gestation length. Over a period of 14 years (2011-2024), the kidding records used in this study were from Boer- and Savanna- (BV; n = 245), Kiko- (K; n = 547), Myotonic- (M; n = 238), and Spanish-sired does (S; n = 487). Each year, does were bred in October or December for kidding in March (n = 960 kidding records) or May (n = 557 kidding records). Chi-square tests were used to compare the actual and expected proportion of does that kidded within the first 7 or 10 days of the start of each kidding season. Kidding records of does that kidded beyond 26 days of the start of the kidding season were excluded from the dataset. A higher (p < 0.01) proportion of does kidded during the first 7 days of the kidding season than expected within each of the doe breed groups (BV: 59.6 vs. 33.5%; M: 53.4 vs. 32.8%; K: 56.5 vs. 32.9%; S: 47.6 vs. 32.9%). A greater (p < 0.01) than expect proportion of does kidded in the first 7 days of the March (58.4 vs. 33.0%) and May (45.4 vs. 33.0%) kidding seasons. The proportion of does that kidded during the first 10 days of the kidding season was also higher (p < 0.01) than expected within each of the doe breed groups (BV: 76.7 vs. 49.8%; M: 68.9 vs. 50.0%; K: 70.2 vs. 49.9%; S: 66.9 vs. 49.9%). Likewise, a higher (p < 0.01) than expected percentage of does kidded in the first 10 days of the March (75.8 vs. 50.0%) and May (60.0 vs. 49.9%) kidding seasons. Preliminary results suggest that a buck effect increased the proportion of does kidding early. The buck effect may allow for shortening the breeding season and reducing the age disparity within a kid crop. Further research on buck-induced estrus in does cycling during the normal breeding season seems warranted.