A short survey of key silage-making practices on Northern Ireland dairy farms, and farmer perceptions of factors influencing silage quality

peer-reviewedNorthern Ireland dairy farmers (n = 174) were surveyed to identify key silage-making practices, and factors perceived to influence the quality of grass silage made on their farms. The majority of farmers (65%) harvested grass for silage three times/year: 62% normally used a contractor, while 47% routinely used a silage additive. Delays to mowing and delays to harvesting due to adverse weather or poor ground conditions were perceived to have a large or very large impact on silage quality (68% and 53% of farmers, respectively). Inadequate wilting, poor-quality swards on owned land, on rented land and “contamination” of first-cut grass with autumn or winter growth herbage were all perceived as having a large or very large impact on silage quality (32%, 27%, 40%, 30% of farmers, respectively). Over the previous decade, 11%, 41% and 37% of farmers claimed a small, moderate or large improvement in silage quality, mainly due to earlier cutting of grass and ensiling better quality swards

Immunological effects of altering the concentrate inclusion level in a grass silage-based diet for early lactation Holstein Friesian cows

Concentrate inclusion levels in dairy cow diets are often adjusted so that the milk yield responses remain economic. While changes in concentrate level on performance is well known, their impact on other biological parameters, including immune function, is less well understood. The objective of this study was to evaluate the effect of concentrate inclusion level in a grass silage-based mixed ration on immune function. Following calving 63 (45 multiparous and 18 primiparous) Holstein Friesian dairy cows were allocated to one of three isonitrogenous diets for the first 70 days of lactation. Diets comprised of a mixture of concentrates and grass silage, with concentrates comprising either a low (30%, LC), medium (50%, MC) or high (70%, HC) proportion of the diet on a dry matter (DM) basis. Daily DM intakes, milk yields and BW were recorded, along with weekly body condition score, milk composition and vaginal mucus scores. Blood biochemistry was measured using a chemistry analyzer, neutrophil phagocytic and oxidative burst assessed using commercial kits and flow cytometry, and interferon-γ production evaluated by ELISA after whole blood stimulation. Over the study period cows on HC had a higher total DM intake, milk yield, fat yield, protein yield, fat+protein yield, protein content, mean BW and mean daily energy balance, and a lower BW loss than cows on MC, whose respective values were higher than cows on LC. Cows on HC and MC had a lower serum non-esterified fatty acid concentration than cows on LC (0.37, 0.37 and 0.50 mmol/l, respectively, P=0.005, SED=0.032), while cows on HC had a lower serum β-hydroxybutyrate concentration than cows on MC and LC (0.42, 0.55 and 0.55 mmol/l, respectively, P=0.002, SED=0.03). Concentrate inclusion level had no effect on vaginal mucus scores. At week 3 postpartum, cows on HC tended to have a higher percentage of oxidative burst positive neutrophils than cows on LC (43.2% and 35.3%, respectively, P=0.078, SED=3.11), although at all other times concentrate inclusion level in the total mixed ration had no effect on neutrophil phagocytic or oxidative burst characteristics, or on interferon-γ production by pokeweed mitogen stimulated whole blood culture. This study demonstrates that for high yielding Holstein Friesian cows managed on a grass silage-based diet, concentrate inclusion levels in early lactation affects performance but has no effect on neutrophil or lymphocyte immune parameters

Tissue-specific differences in insulin receptor m-RNA isoform ratio in two dairy cow breeds

The insulin receptor (IR) is one participant in the partitioning of absorbed nutrients to, and between, the insulin-responsive tissues of animals. We previously reported the alternative splicing of a 36 base pair exon 11 segment of the sheep IR gene and found differences in the ratio of the resultant 11 m-RNA and 11+m-RNA isoforms between muscle and fat depots in crossbred, but not purebred, Texel lambs (McGrattan et al., 1998). Because the IR isoforms, when expressed in cultured cell lines, differ in affinity for insulin by two fold or more (McClain, 1991), variations in the ratio of IR isoform expression may have practical significance for the partitioning of nutrients between tissues and thus for differences in lean and fat gain between the purebred and crossbred lambs. Similarly, variation in IR m-RNA isoform ratios amongst the adipose depots in different breeds of dairy cow could have practical significance for differences in the ability of the breeds to store and mobilise energy and thus for differences in lactational performance between dairy breeds. This study is a preliminary investigation of this hypothesis.</jats:p

The effect of silage quality and frequency of feeding of supplementary concentrates on serum metabolite and insulin-like growth factor 1 (igf-1) concentrations in the late pregnant ewe

Concentrates for pregnant ewes are often increased incrementally during the last 6-8 weeks to as much as 50% of dry matter intake. Commonly, they are given as a single daily feed. Increasing the number of meals in which a concentrate allowance is given to cattle minimises diurnal fluctuation in ruminal activity with beneficial effects on dry matter intake (DMI).The current study was undertaken to determine if more frequent feeding of concentrates to ewes in late pregnancy affects levels of nutritionally-dependent serum IGF-1 and serum metabolites and to associate these with changes in ewe DMI and performance.</jats:p

Evidence for tissue-specific alternative splicing of the ovine insulin receptor gene

Alternative splicing of a discrete 36 base pair segment (exon 11) of the human and rat insulin receptor leads to the formation of high and low affinity isoforms differing as much as 3-fold in affinity for insulin. Alternative splicing is a common mechanism for generating protein isoforms and is often regulated in a tissue-specific fashion (Seino &amp; Bell, 1989; Mosthafet al., 1990). In humans, the lower affinity (B-isoform) mRNA transcript is predominantly expressed in tissues that are important for modulating glucose homeostasis such as the liver and muscle whereas the higher affinity (A-isoform) mRNA transcript is predominantly expressed in haematopoietic tissues such as spleen. Alternative splicing of the region of the ovine insulin receptor gene encoding exon 11 has recently been demonstrated (McGrattanet al., unpublished). The objective of the present study was to establish whether tissue-specific regulation of alternative splicing of the insulin receptor gene occurs in the ruminant animal.</jats:p