Does Size Matters? Relationships among Social Dominance and Some Morphometric Traits upon Out-of-Season Reproductive Outcomes in Anestrus Dairy Goats Treated with P4 + eCG

Abstract

The possible role of the social rank (R) (i.e., low-LSR, middle-MSR, or high-HSR) in anestrus goats exposed to a P4 + eCG (D) (i.e., 100 or 350 IU) estrus induction protocol (EIP) was evaluated. Goats (Alpine-Saanen-Nubian × Criollo; n = 70; 25° North) managed under stall-fed conditions were all ultrasound evaluated to confirm anestrous status, while the social rank was determined 30 d prior to the EIP. The response variables included estrus induction (EI, %), duration of estrus (DUR, h), ovulation rate (OR, n), live weight (LW, kg), thoracic perimeter (TP, cm), thoracic diameter (TD, cm), body length (BL, cm), height at withers (HW, cm), beard length (BEA, cm), compactness index (COM, cm), and anamorphosis index (ANA, cm), as affected by R, D, and the R × D interaction were evaluated, while the correlation coefficients among reproductive and morphometric variables were quantified. An R × D interaction (p < 0.05) affected the response variables EI, DUR, and OR. While the largest (p < 0.05) EI% occurred in the HSR goats, irrespective of eCG (i.e., 100 or 350 IU), both the shortest estrus duration (DUR, h) and the lowest ovulation rate (OR, n) occurred in the LSR + D100 combination, with no differences among HSR and MSR either with D100 or D350. Regarding the LW and morphometric response variables, (i.e., LW, TP, TD, BL, HW, BEA, COM, and ANA) all of them favored either the HSR and MSR groups, with the lowest phenotypic values occurring in the LSR-goats. The EI% was observed to be positively correlated (p < 0.05) with DUR (0.71), LW (0.28), TP (0.31), TD (0.34), BL (0.33), HW (0.35), COM (0.23), and ANA (0.23). While DUR was correlated (p < 0.05) with TP (0.26) and ANA (0.24), OR demonstrated no-correlation (p > 0.05) with any response variable, either reproductive or morphometric. As expected, LW had high correlation coefficients (p < 0.01) with TP (0.86), TD (0.88), BL (0.82), HW (0.75), BEA (0.51), COM (0.97), and ANA (0.75). In general, the morphometric variables as a whole demonstrated important correlation coefficients among them (p < 0.01), ranging from 0.38 up to 0.84. To estimate the importance of the morphometric differences between social rank upon estrus induction, a principal component (PC) analysis was performed based on the correlation matrix derived from the corporal measurements. The PC1 and PC2 explained 70.3% and 17.6% of the morphometric variation, respectively. The PC1 was a measure of the goat size (i.e., small, medium, large) and its association with estrus occurrence was evaluated using a logistic regression model; the bigger the goat, the increased probability of being in estrus, by up to five times compared to small goats. Our results confirm that the higher social ranked, larger goats amalgamated some fundamental factors to be successful: aggressiveness, primacy to food access, augmented live weight, and corporal size; all of these were able to modulate out-of-season reproductive success in crossbred dairy goats subjected to an estrus induction protocol and managed under stall-fed conditions in Northern Mexico.

Genome-wide association analysis of nine reproduction and morphological traits in three goat breeds from Southern China

“…Some of the goats under investigation were found to have long beards while others have short beards. A study in anestrus dairy goats evaluated some morphometric traits including beard length, for exploring the possible role of these traits in goat reproductive success [ 31 ]. Such morphometric advantages shown by the high social rank goats emphasized the need for comprehending the biological basis of relevant animal traits and yet, the genetic mechanism of beard length remains unclear.…”

An Enhanced Body Condition Improved Sexual Behavior, Ovarian Structure and Function, and Reproductive Fitness in Rangeland-Crossbred Dairy Goats

“…According to Mellado et al, the kidding rates of goats with a low BCS (i.e., three (range 1-7)) were about 20% lower than goats with a BCS higher than four [40]. Goats with a higher BCS, in addition to their larger size, stimulate increased sexual behavior in bucks, and are positively related with a higher ovulation rate and a larger luteal diameter and volume [12]. Such a scenario can promote increased progesterone production [31] and should contribute to the maintenance of pregnancy and a greater number of live-born kids.…”

“…Additionally, high BCS bucks exert a greater number of sexual behaviors, such as lateral approaches, anogenital sniffing, mounting attempts, self-marking, flehmen, and mounting with intromission [11]. Also, and quite interesting, larger female goats depicting a higher hierarchy within the herd and positively related to BCS show an augmented estrus latency, as well as increased sexual behaviors regarding the subordinated goats [12]. Based on the findings obtained at this latitude and with similar goat genotypes, we hypothesize that on one side, bucks exposed to high BCS-females exert more frequent sexual behaviors, and positively influence the diameter and volume of some ovarian structures aligned with augmented reproductive outcomes regarding low-BCS goats.…”

A Circular Economy Approach to Integrate Divergent Ruminant Production Systems: Using Dairy Cow Feed Leftovers to Enhance the Out-of-Season Reproductive Performance in Goats

“…However, reproductive seasonality may vary according to breed, showing dissimilar reproductive responses at different latitudes; native goats to tropical areas may show low or non-reproductive seasonality [2]. Moreover, sexual behavior and reproductive outcomes can be modulated through hormonal treatments [3], sociosexual interactions [4], hierarchical structures within the herd [5], and nutritional status, which results in different body condition scores (BCS) for the animals [6,7]. In the arid and semi-arid zones of Northern Mexico (25 • N), most goats are kept in rangeland, which presents drastic feed fluctuations, either in regard to quantity or quality; therefore, the nutritional supplementation of goats is generally required to maintain an adequate reproductive performance [8].…”