RESUMO
Adding gelling agents to convert the liquid state of the semen extender to a solid state allows for an increased sperm life span. Gelatin and alginate have been used to study the effects of gelling agents on sperm quality. However, there are other gelling agents that have not been studied, such as agar. In addition, studying different sources of gelling agents or the effect of mixing more than one gelling agent with semen extenders on sperm fertility has received little attention. Therefore, the objective of this study was to evaluate the effect of adding agar and a mixture of gelling agents from different sources to semen extender on ram sperm traits and fertility. The first trial evaluated the effect of the addition of 2.5-3 mg mL-1 of gelatin mixed with 0.5-20 mg mL-1 of agar or alginate to ram semen extender on sperm (motility, progressive motility, live/dead, membrane integrity) and semen (pH) characteristics. The response variables were evaluated 1, 72 and 144 h after storage at 4°C. In the second trial, two sources (feed grade and bacteriological) of gelatin and agar were evaluated on the response variables as in Trial 1. In trial 3, a total of 34 ewes were inseminated with doses supplemented (n = 17) with or without (n = 17) agar and gelatin. The pregnancy rate was diagnosed 40 days after insemination. In general, adding agar and gelatin improves (p < .05) sperm motility, membrane integrity and the ratio of live sperm after 144 h of storage compared to the Control group, regardless of the source (bacteriological or feed grade). However, the pregnancy rate in ewes was not influenced (p ≥ .05) by semen doses stored with agar and gelatin. In conclusion, the addition of agar and gelatin preserves ram sperm motility and membrane integrity after 144 of storage at 4°C without affecting the pregnancy rate in inseminated ewes.
RESUMO
This paper aims to review, systematically synthesize, and analyze fragmented information about the importance of coat color in local goats and its relationship with productivity and other important traits. Topics on current research on color expression are addressed, the relationship that has as a mechanism of environmental adaptation, its relationship with the production of meat, milk, and derivates, and the economic value of this characteristic. The use of this attribute as a tool to establish selection criteria in breeding programs based on results reported in the scientific literature is significant, particularly for low-income production systems, where the implementation of classic genetic improvement schemes is limited due to the lack of productive information, which is distinctive of extensive marginal or low scaled production systems around the world.
RESUMO
The aim was to evaluate the pre-weaning productive performance and growth curve of Dorper*Katahdin (DPr; n = 46), Kathadin*Kathadin (KTn; n = 204) and Romanov*Kathadin (RMv; n = 40) of commercial crossed lambs from central Mexico. We considered 1450 data from 290 crossbred lambs. The variables contemplated in this study were cross (CR), lambing type (LT), sex, birth weight (BW), weaning weight (WW), test days (TD), and daily weight gain (DWG). Correlation analysis and adjustment of growth curve were performed. Differences in CR and sex were found only in BW (p < 0.05). No differences in DWG, WW, and TD (p > 0.05) by CR and sex were found. Single lambing had the highest (p < 0.05) BW, WW, and DWG. Phenotypic correlations differ among crosses. Lambs crossed with DPr presented the highest values in parameters a and b and the lowest in c. The productive behavior of DPr, KTn, and RMv cross with KTn lambs in central Mexico is similar in the pre-weaning period; however, the growth curve and parameters that characterize it suggest that DPr lambs show a tendency to enhance productive behavior in this period.